Here’s what Raptgo says about it:
“The problem with many PZT drivers is their low output, resulting in ineffective contribution of the driver to the overall sound. Using Raptgo’s proprietary SSCE (Sound Superposition Compensation Effect) technology, the air conduction driver is powered in succession with the PZT driver for a more effective bone conduction. This provides a superior PZT driver effect that can truly be experienced for the first time.”
They claim that the PZT acts with the 6mm dynamic to create superpositioned waves.
https://www.acs.psu.edu/drussell/demos/superposition/superposition.html
The Linsoul page has more details.
https://www.linsoul.com/blogs/announcements/raptgo-bridge-new-tribrid-iem-release-at-linsoul-audio
As usual, who knows how legitimate any of this is, but they’re certainly doing
something. The Bridge sounds different than anything else in my collection.